Ethene methoxycarbonylation

Heterocycles Both non-aromatic unsaturated heterocycles and heteroaromatic compounds are able to play the role of ethene dipolarophiles in reactions with nitrile oxides. 1,3-Dipolar cycloadditions of various unsaturated oxygen heterocycles are well documented. Thus, 2-furonitrile oxide and its 5-substituted derivatives give isoxazoline adducts, for example, 90, with 2,3- and 2,5-dihydro-furan, 2,3-dihydropyran, l,3-dioxep-5-ene, its 2-methyl- and 2-phenyl-substituted derivatives, 5,6-bis(methoxycarbonyl)-7-oxabicyclo[2.2.1]hept-2-ene, and 1,4-epoxy-l,4-dihydronaphthalene. Regio- and endo-exo stereoselectivities have also been determined (259). 

However, the complex [Pd(dppomf)(COCH3)]+ undergoes immediate methanolysis at room temperature and even though (1) the dppomf acts as a tridentate 3-P, P, Fe ligand, with trans P atoms, and (2) ethene does not insert, which is indicative that a coordination site is not easily available. Thus, in this case, methanolysis either occurs via a five-coordinate transition state or it can occur also intermolecularly [47]. This might be also the case for the methoxycarbonylation of ethene catalysed by the osmocene analogue of dppf (Sect. 3.3.2) [79]. 

From what is reported above, it is evident that the CO-ethene copolymerisation and the methoxycarbonylation of ethene are closely related. In principle the mechanisms discussed for the copolymerisation process are valid also for the case when termination occurs after the insertion of just one molecule of each monomer into the species that initiate the catalysis, Pd-OCH3+ or Pd - H+. These species can form as schematized by Eqs. 10-16. The copoly-... 

Recently, it has been reported that Pd(II) complexes with ferrocenyldiphos-phines 33, are also efficient catalysts for the selective methoxycarbonylation of ethene with activity comparable to that of the dtbpx-based system (initial TOF = 30000 h-1, TON = 60000, at 100 °C, lObar) [139,140]. 

For the industrially important Pd-catalyzed methoxycarbonylation of ethene to methyl propanoate, all the intermediates of the cycle have been identified. Starting from 34, CH2=CH2 and CO, the process has been shown to proceed via a hydride rather than a methoxycarbonyl cycle (Scheme 1.1) [25][26]. Figure 1.9 shows the P NMR spectrum at 193 K of a 1 1 mixture of the two isotopomers 35a and 35b, formed in the reaction of 34 with CH2= CH2- The presence of an agostic interaction is supported by the C chemical shifts ( (CHj) 31, and (CHj) 8), which are reversed with respect to classical Pd-ethyl complexes. 

Scheme 1.1 The two possible mechanisms for the Pd-catalysed methoxycarbonylation of ethene.

The cationic Pt(ii) hydride 78 [27], a model for the analogous Pd intermediate which is thought to be involved in the methoxycarbonylation of ethene (see Scheme 1.1 and Figure 1.10), also shows the expected markedly different J( P, H) values. 

In Gegenwart von sek. Aminen (z. B. + -tp-Ephedrinen) reagiert 3-Methoxycarbonyl-1-oxo-1,3-dihydro-2-benzofuran mit 2-Nitro-1-phenyl-ethen zu l-Methoxycarbonyl-l-(2-ni-tro-l-phenyl-ethyl)-3-oxo-l, 3-dihydro-2-benzofuran ( 100%) ... 

Bianchini C, Meli A, Oberhauser W, Zuideveld MA, Freixa Z, Kamer PCJ, Spek AL, Gusev OV, Kalsin AM (2003) Methoxycarbonylation of ethene by palladium(II) complexes with l,l -bis(diphenylphosphino)ferrocene (dppf) and l,l -bis(diphenylphosphino)octamethyl-ferrocene (dppomf). Organometallics 22(12) 2409-2421. doi 10.1021/om021049b... 

Pugh RI, Drent E (2002) Methoxycarbonylation versus hydroacylation of ethene dramatic influence of the ligand in cationic palladium catalysis. Adv Synth Catal 344(8) 837-840. doi 10.1002/1615-4169(200209)344 8 <837 aid-adsc837>3.0.co 2-l... 

Methoxycarbony]-ethen- -diethylester XII/1, 437 1-Methoxycarbonyl-l-methyl-ethan- -dimethyl-... 

Bis[tetraphenylphosphonium] bis[l,4-tetratellurido]oxomolybdate(IV) reacted with dimethyl acetylenedicarboxylate in acetonitrile to produce the phosphonium salt of bis [1,2-bis(methoxycarbonyl)ethene-l, 2-ditellurolato]oxomolybdate(IV). Elemental tellurium... 

Ethen l-Chlor-l-(methoxycarbonyl-methyl-amino)-2-phenyl- E15/3, 3292 (CO-Cl COOR)... 

Obtained from active methylene compounds, such as malonic esters, -0x0 esters and jS-oxo sulfones, iodonium ylides serve as precursors of the corresponding carbenes. Their decomposition by a catalytic amount of a copper salt in the presence of a C-C double bond has been used for inter- and intramolecular cyclopropanation reactions. Thus, reaction of cyclohexene with bis(methoxycarbonyl)methylene(phenyl)iodine(III) under the catalytic action of bis(acetylacetonato)copper(II) yielded dimethyl bicyclo[4.1.0]heptane-7,7-dicarboxylate (1) (38%, mp 91-93°C) in addition to tetrakis(methoxycarbonyl)ethene (41%). ... 

Dimethyl (cyclohex-2-enyl)malonate (6%) and tetrakis(methoxycarbonyl)ethene (12%) were also formed. With trimethyl phosphite/ copper(I) iodide, the yields were 74, 6 and 12%. 

There is much current industrial interest in the palladium-catalysed methoxycarbonylation of ethene to give methyl propanoate (MeP), the precursor to methyl methacrylate. The Pd° catalyst precursor contains a novel bis(phosphine), for example, l,2-(CH2PBu 2)2C6H4, and, under reaction conditions, gives MeP with high turnover and selectivity (99.98%). We have inves-... 

The convenient synthesis of a-hydroxyl-co-methoxycarbonyl asymmetric telechelic PIBs has been achieved by the combination of two recently discovered techniques, haloboration-initiation and end capping with 1,1-diphenylethylene followed by end quenching with silyl ketene acetals, 1 -methoxy-1 -trimethylsiloxy-2-methyl-propene (MTSMP), 1-methoxy-1-trimethylsiloxy-propene (MTSP), and 1-methoxy-l-trimethylsiloxy-ethene (MTSE). Nearly quantitative chain end functionalization has been proved by NMR, quantitative NMR, and FT-IR spectroscopy. The methoxycarhonyl end arising by quenching with MTSMP could not be hydrolyzed under either basic or acidic conditions. These methods also failed to yield the acid when the corresponding diisobutylene derivative was used. The sterically less hindered esters, however, readily underwent hydrolysis resulting in the formation of a-hydroxyl-co-carboxyl asymmetric telechelic PIBs. 

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